1. Field of the Invention
The invention relates to deoiled phosphatides; food grade or pharmaceutical grade lecithin; and methods for producing same.
2. Related Art
The mixture of phosphatides referred to as lecithins is a mixture of naturally occurring fat soluble derivatives composed of the following structural members: glycerol, fatty acids, phosphoric acid, amino alcohols and carbohydrates. They are found in practically any animal and vegetable material. Commercial lecithin refers to this phospholipid mixture which is generally obtained by hydrating with water and removing the resultant gums formed by centrifugation from neutral triglyceride oil. One of the primary sources of lecithin is crude soybean oil.
Other oil bearing seeds such as corn germ and rapeseed yield lecithins, but are of lesser importance commercially. Lecithin produced by drying the gums contains 25-35% neutral triglycerides and 65-75% phosphatides, and is a plastic or viscous fluid product. This 65-75% phosphatides is referred to as 65-75% AI (acetone insolubles) due to the fact that in general the phosphatide fraction is insoluble in acetone. It is tested using AOCS (American Oil Chemists' Society) Method Ja 4-46.
In many applications, a solid granular or powdered product is desired. Such a product can be made by removing the neutral triglyceride oil from the lecithin. The art separates the oil by extracting with acetone ("Lecithins", B. Szuhaj and G. List, American Oil Chemists Society, 1985) and this is referred to as acetone deoiling. Until now, acetone deoiling has been the only commercially viable process for such preparation. Acetone deoiling suffers problems, however, in that as a solvent, acetone has a degree of toxicity. Additionally, residual amounts of acetone can remain in deoiled lecithin at levels of 5-10 ppm after desolventizing. Furthermore mesityl oxide, an acetone condensation product, can be present which imparts a significant off flavor. The acetone deoiled product must be analyzed routinely to carefully monitor both acetone and mesityl oxide residuals.
Because of the disadvantages associated with acetone extraction, alternative methods have been considered for processing of crude lecithin, such as using extraction with hydrocarbons (3-4 carbon atoms) under pressure (1-8 Mpa) with temperatures of from 20-100.degree. C. (U.S. Pat. No. 5,597,602). Also the use of high pressure carbon dioxide has been suggested (DE-A 30 11 185).
Lipids may be separated from non-lipids and neutral lipids may be separated from polar lipids, especially phospholipids can be separated from neutral triglycerides using non-polar solvents and membrane separation. Non-polar solvents such as hexanes, chlorinated hydrocarbons, ethyl acetate may be separated from micelles with phospholipids which have molecular weights less than 50,000 daltons. These micelles act like macromolecules and are impermeable to ultra-filtration forming a retentate. They can thus be separated from the triglycerides which behave as single low molecular weight molecules in solution and pass through or permeate the membranes.
Phospholipids themselves may also be separated from one another in a similar manner using solubility and ultrafiltration techniques with more polar solvents such as alcohols.
Phospholipids have been separated from other components of crude vegetable oils. (U.S. Pat. No. 4,496,489, U.S. Pat. No. 4,062,882 and U.S. Pat. No.4,533,501). For example, there are several methods that exist for refining crude soybean oil (British Patent No. 1,509,543, U.S. Pat. No. 3,878,232). There is also a process (British Patent No. 1,509,543) in which a crude hexane extract of the soybean, soybean oil miscella, is ultra-filtered under pressure through a suitable semipermeable membrane that allows the passage of a glyceride oil solution in hexane, but retains all the phospholipids together with sugars, sterol glucosides, etc., which form co-micelles with phospholipids in hexane solution. This process allows, a separation of phosphorous free lipids (e.g., triglycerides) from phospholipids and non-lipids (e.g., sugars) associated with them. The removal of hexane from the ultra-filtrate yields an oil free of phosphatides, whereas the retentate miscella yields commercial lecithin after hexane is removed.
None of the methods currently being used result in as pure or desirable a food grade lecithin as the process of the claimed invention because the known methods result in lower quality deoiled lecithin that can have an off flavor. Additionally, for currently produced lecithin including deoiled lecithin chemical bleaching agents much as hydrogen peroxide must be used to produce an acceptable light colored product. Therefore, the claimed process is easier to use for the commercial preparation of deoiled food grade lecithin.